With every mass shooting in the United States comes renewed fear of another.It's a fear particularly potent among parents of young children and especially now, days away from the start of the school year. It's not unwarranted -- CNN examined 10 years of shootings on K-12 campuses and found two sobering truths: School shootings are increasing, and no type of community is spared.Instead of letting their children choose a plastic backpack covered in Hello Kitty or Spider-Man, some parents are purchasing bags that double as shields in case kids get caught in gunfire.

Companies like Guard Dog Security, Bullet Blocker and TuffyPacks designed bulletproof backpacks to quell those concerns.The retailers said backpack sales spike during the back-to-school season, and all three said they they saw a significant uptick in the aftermath of mass shootings.